using System;

​

using System.Linq;

using System.Collections.Generic;

​

// EF 6.0 POCO

public partial class Message

{

    //public Message()

    //{

    //    this.MessageConsumers = new List<MessageConsumer>();

    //    this.ResponseLogs = new List<ResponseLog>();

    //}

​

    public int MessageId { get; set; }

    public int FipMethodId { get; set; }

    public int F_Id { get; set; }

    public string FenergoUserName { get; set; }

    public string MessageXml { get; set; }

    public System.DateTime InsertDate { get; set; }

    public int MessageStatusId { get; set; }

    public int ProductId { get; set; }

}

​

​

public class Program

{

    public static void Main()

    {

        // fakes

        var Messages = new List<Message>();

        // Query 1

        var v1 = 

            from m in Messages

            where m.MessageStatusId < 5 && (    

            from mm in Messages

            where mm.MessageStatusId < 5

            group mm by mm.F_Id into g

            select g.Key

        ).Contains(m.F_Id)

        select m;

​

        // Query 2

        var v2 = Messages

                    .Where ( m => 

                                ((m.MessageStatusId < 5) && 

                                Messages

                                  .Where (mm => (mm.MessageStatusId < 5))

                                  .GroupBy (mm => mm.F_Id)

                                  .Select (g => g.Key)

                                  .Contains (m.F_Id)

        ));

​

        // Query 3

​

        var v3 = 

            from mm in Messages

            where mm.MessageStatusId < 5

            group mm by mm.F_Id into g

            from m in g

            select m;

​

​

        // Query 4

​

        var v4 = Messages

                    .Where (mm => (mm.MessageStatusId < 5))

                    .GroupBy (mm => mm.F_Id)

                    .SelectMany (

                        g => g, 

                        (g, m) => m

                    );

    }

}